Calling Refrigeration Techs

[SS MAYFLOAT]

Odd Problem

I've got a 2 door wall freezer. 14" deep, 4' wide, 3' tall. The top, back, and sides normally frost up. This is not frost free and does not have any circulating fans. Normal operating temps are -10 to 0 degrees F.

This unit is 28 years old. TXV was changed 5 years ago when a new 1/3hp condenser unit installed. From that time, this unit has worked flawlessly until now. The left side and back has good frost build up but the top and right end is not freezing. It is not low on refrerant as the sight glass is full, and the head pressure is well within the temp/pressure chart. Condenser coil is spotless as it was cleaned.

From the TXV it seperates into two circuits. One takes care of the left side and back. The other circuit takes care of the top and right side. At first I thought maybe that circuit that was not freezing could have been oil logged or clogged. So, I pumped the unit down, cut the lines to the circuit causing problems. I hooked up my nitrogen tank to the lines and purged the circuit. I only got a slight amount of oil (half a teaspoon) out and it was clean. There was no blockage at all.

I hooked everything back up only for it to repeat the problem. So, today I called the factory tech. He said he never heard of one doing what I described to him.

I mentioned to him that the left side and back had not been defrosted and brought to room temperture. I told the manager to unload (which they were instructed not to use the freezer, but did anyway) the freezer tonight and leave the doors open. Then I will be in first thing in the morning to turn it on and monitor it. The factory tech and I are thinking that with the back and side having ice on them is keeping the unit unbalanced. So hopefully with the unit being brought to room temp will allow the system to balance when turned on. I just hope this is the problem.

If this does not fix the problem, the only other recourse that I can think of doing is putting two new TXV's on. One for each circuit. However, I feel I shouldn't have to do this as it has worked fine for the past 5 years with the new TXV and condenser. The unit is charged with Hotshot R414B which was used when the new condenser was installed.

I've been doing this work for over 25 years and never came across a problem like this. Any thoughts or ideas? Thanks.......SS

 

[j_martin]

Re: Calling Refrigeration Techs

What's the distribution to the 2 evap circuits. Cap tube or expansion valve?

 

[Tim Frank]

Re: Calling Refrigeration Techs

OP said there is a TXV.

I would say put in a manual balancing valve where the two circuits split off....or the dual TXVs...whatever is easier. Results should be the same either way.
Probably should have been piped that way when original repair was made.

Odd this would suddenly happen after 5 years though. Any recent weather anomoly?

 

[j_martin]

Re: Calling Refrigeration Techs

Usually with multiple loads on a single pump, a separate expansion valve is used on each circuit, and it will self balance.

If yer feeding essentially 2 load with 1 valve, then if it worked, you were lucky. When someone loaded some warm product in one side, the refrigerant flopped to the cold side and stayed there.

If you put in a valve for each coil, it'll autobalance.

I'm not a refrig tech per se, but I earned my living for awhile in phase change thermodynamics design.

 

[SS MAYFLOAT]

Re: Calling Refrigeration Techs

OP said there is a TXV.

Any recent weather anomoly?

Yes, we have had lots of rain. The humidity is real high. In another store they don't seem to get the idea that the door on the walkin cooler is to keep the box cool. So the evap coil turns into a big block of frost. Thanks,, I'm headed off to work now. WIll let you know how it performs today....SS

 

[SS MAYFLOAT]

Re: Calling Refrigeration Techs

The unit was turned on this morning. Within 20 minuets all panels frosted up. This afternoon when I clocked out, I went and checked on the unit. I found product holding the door open with the top and side defrosted. This unit is mounted to the wall just left of our fryers. Lots of hot air rises up right into the freezer cabinet. Guess I'm going to have to teach teens how to keep a door closed or bite the bullet and put another TXV in. This problem coincides with the hiring of the new fry person. Go figure? ........SS

 

[Rscardina]

Re: Calling Refrigeration Techs

Sounds like the TXV is hunting... you should not need 2 txvs to balance anything... the compressor suction will do that for you..

if they frost immediately then chances are a block in the txv or a bad txv cap.

does the existing txv have an equalizer port? if so this should also be checked
it should be tapped just after the evaps..

lastly, what method of charging are you using? approach? weight? supperheat?

Last but not least....what are your suction and discharge pressueres? another casue could be bad valves in the compressor.. the only way to prove that is if you can isolate and let it pump down itself.. it should hit -30 vaccum easily...if not..then consider the compressor is bad

 

[Tim Frank]

Re: Calling Refrigeration Techs

Sounds like the TXV is hunting... you should not need 2 txvs to balance anything... the compressor suction will do that for you..

if they frost immediately then chances are a block in the txv or a bad txv cap.

does the existing txv have an equalizer port? if so this should also be checked
it should be tapped just after the evaps..

lastly, what method of charging are you using? approach? weight? supperheat?

Last but not least....what are your suction and discharge pressueres? another casue could be bad valves in the compressor.. the only way to prove that is if you can isolate and let it pump down itself.. it should hit -30 vaccum easily...if not..then consider the compressor is bad

Didn't see any evidence of "hunting" in OP's post.

What has been explained so far is that there is a repeating imbalanced load on the evaporator circuits (high external humidity and a liveware issue that causes an increased load on the circuit beside the fryer/door) which would lead to the exact symptoms exhibited. I bet the suction pressure is lower than normal as well.
The textbook solution is to balance the load and correct the refrigerant distribution....it is also the practical solution as well.

Sounds like SS has it nailed!

 

[Rscardina]

Re: Calling Refrigeration Techs

The textbook solution is to balance the load and correct the refrigerant distribution....it is also the practical solution as well.

Sounds like SS has it nailed!

Agreed, but the text book doesnt know that this ran for 5 years with no issues. 1 txv for two circuits is perfectly fine.. the compressor suction will balance, as it pull equally from both evaps. the only difference is if either one gets restricted.. both circuits act as one if the bulb is in the correct spot..

I dont mean to be stubborn, but adding another txv may help in keeping the unbalanced load from screwing up operations when fry boys cant shut a darn door..but seriously? tell him to keep the door shut!

since it was claimed that there is high humidity and such..I was wondering if the door gaskets are good??

 

[Tim Frank]

Re: Calling Refrigeration Techs

Agreed, but the text book doesnt know that this ran for 5 years with no issues. 1 txv for two circuits is perfectly fine.. the compressor suction will balance, as it pull equally from both evaps. the only difference is if either one gets restricted.. both circuits act as one if the bulb is in the correct spot..

I dont mean to be stubborn, but adding another txv may help in keeping the unbalanced load from screwing up operations when fry boys cant shut a darn door..but seriously? tell him to keep the door shut!

since it was claimed that there is high humidity and such..I was wondering if the door gaskets are good??

I don't really disagree with you, but I don't think you are being realistic. I'm not sure how "good " a gasket can be if the door is not closed....

History is of no consequence if the operational reality is that the door will be left open on a regular basis. OP has been asked for a solution....that would be fixing the problem such that the service call does not amount to a visit and the advice that the door needs to be kept closed.

Unless "Keep the door closed and don't call me again" is an option.

 

[Rscardina]

Re: Calling Refrigeration Techs

I'm not sure how or if this got resolved but I would be interested in knowing.

Yes, a gasket does no good with the door open..but if the door will be open more now than before then i would suggest curtains installed if space is available.. (seemed small from the diimensions) but you can at least you slow the transfer of heat to cool when its open..



let me know how this ends

Thanks

 

[SS MAYFLOAT]

Re: Calling Refrigeration Techs

The problem is still not resolved. I'm not too keen on installing another TXV. If the unit was engineered for only one and it has worked for all these years,,,,,,it should work now.

The door gasket is not in bad shape. I've seen a lot worse. These units we use will frost the coil even if the door is left open all day. The proble here is one side is not frosting.

I thought of another problem that I had with a gas fryer. The fryer was a Frymaster with two burners. The right side would have a blue flame while the left side would burn nice and bright orange. It was not the gas valve, pilot, ignition, venter motor, or the right side burner. It was the left side burner as it had several cracks. This allowed more air to be sent to that side.

Using the above problem of the fryer, I'm thinking that just because the left side seems to be fine, could it be the problem? I didn't cut into that side to blow it out with nitrogen. Probably should have. I only get about a 3 hour window to work on this unit as the store is open and operating. Sure is a pain to have all my equipment out with the workers bumping into me, the ladder, and kicking my gear around. Plus this is not accounting the fact that I'm working just above the fryers which means I've got to ensure no dirt or contaiminates gets into them (especially dropping a tool or screws into them).

I will get to be able to work on this unit Tuesday morning this week. I'm going to put on a new TXV on the system or just replace the power head to it. Cut the lines and blow both sides out again.

It sure is funny how a person can spend many years servicing equipment and still always come up with different problems that has never been encountered.

Monday morning I have another freezer that has a bad TXV. Not looking forward to changing it. It was mounted on the unit from the backside. Problem is it is a permanent unit fastened to the wall. It is soldered in with the line set against the wall and located back behind the counter shelves under the wall freezer. I'll have to get into a space 18" wide, 30" high" and about 36" back. The engineers sure didn't think about future servicing when they designed that one. Hopefully I can take my plasma and cut a hole in the side to get better access. I'm not thrilled about dealing with the heat, smoke, and fumes from the torch.

I'll give an update on what I find from Tuesdays problem. Thanks.......SS

 

[SS MAYFLOAT]

Re: Calling Refrigeration Techs

I installed new door gaskets and got the superheat adjusted. Unit is working fine at this point. Plus new fry person has got the message to make sure the door is completely shut or he will be put on dishwasher duty.